When any constricted part arises in a lumen in the body, such as a bile duct, blood vessel, trachea, esophagus and urethra, a medical treatment of placing a stent at the constricted part to secure the lumen in the body has been given. A stent normally has a tube shaped body having an adjustable outer diameter and is inserted to a lumen in the body while the outer diameter is adjusted to be small (a contracted state), positioned at a constricted part, where the outer diameter is made larger (an expanded state), and placed to secure the lumen of the constricted part.
In the stent, it is known that the structure (design) of a tube wall thereof largely affects various capabilities, and variously designed stents have been developed. For example, the patent article 1 discloses a stent, wherein the tube wall is configured by a threadlike material (web pattern) having a zigzag shape formed continuously in the circumferential direction.
The stent in the patent article 1 has excellent flexibility when in a contracted state, so that it can be inserted easily to a lumen in the body, furthermore, the expanded state is easily maintained, so that it has an excellent capability of securing the lumen in the body.
However, the stent in the patent article 1 has a possibility of damaging an inner wall of the lumen in the body by edges of turned edge portions of the zigzag-shaped threadlike material when expanding in the lumen in the body. When a lumen in the body is damaged by a stent, not only damaging the lumen in the body, a phenomenon (ingrowth) that biologic tissue passes through interspaces of the stent and enters into the stent to occlude the lumen in the body is easily caused as well.
Also, in some cases, a film (a cover film) formed by a synthetic resin, etc. is wound when using the stent for a purpose of securing a lumen in the body more surely. However, if a film is wound when using the stent in the patent article, edges of the turned edge portions of the zigzag-shaped threadlike material may stub the film to break the film at the time of expanding in a lumen in the body.
Patent Article 1: The Japanese Patent Publication No. 2002-524135